[PATCH] PCI: mediatek: Fix integer truncation in fls() for resource size

[PATCH] PCI: mediatek: Fix integer truncation in fls() for resource size

[Sreeraj S Kurup]

resource_size() returns a resource_size_t, which is 64-bit on 64-bit
architectures or 32-bit systems with LPAE/PAE enabled. Passing this
directly to fls(), which accepts an unsigned int, implicitly truncates
the upper 32 bits.

If a memory resource window of 4 GiB or larger is passed, the size
truncates to 0, resulting in invalid AHB-to-PCIe translation window
sizes.

Fix this by using fls64() to safely handle 64-bit resource sizes.

Signed-off-by: Sreeraj S Kurup <sreekuttan2156239@gmail.com>
---
 drivers/pci/controller/pcie-mediatek.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/controller/pcie-mediatek.c b/drivers/pci/controller/pcie-mediatek.c
index a60d1ae076f8..61591d0176bc 100644
--- a/drivers/pci/controller/pcie-mediatek.c
+++ b/drivers/pci/controller/pcie-mediatek.c
@@ -8,6 +8,7 @@
  */
 
 #include <linux/bitfield.h>
+#include <linux/bitops.h>
 #include <linux/clk.h>
 #include <linux/delay.h>
 #include <linux/errno.h>
@@ -754,7 +755,7 @@ static int mtk_pcie_startup_port_v2(struct mtk_pcie_port *port)
 
 	/* Set AHB to PCIe translation windows */
 	val = lower_32_bits(mem->start) |
-	      AHB2PCIE_SIZE(fls(resource_size(mem)));
+	      AHB2PCIE_SIZE(fls64(resource_size(mem)));
 	writel(val, port->base + PCIE_AHB_TRANS_BASE0_L);
 
 	val = upper_32_bits(mem->start);
@@ -830,7 +831,7 @@ static int mtk_pcie_startup_port_en7528(struct mtk_pcie_port *port)
 
 	/* Set AHB to PCIe translation windows */
 	val = lower_32_bits(mem->start) |
-	      AHB2PCIE_SIZE(fls(resource_size(mem)));
+	      AHB2PCIE_SIZE(fls64(resource_size(mem)));
 	writel(val, port->base + PCIE_AHB_TRANS_BASE0_L);
 
 	val = upper_32_bits(mem->start);
-- 
2.55.0